Derivative Instruments and Hedging Activities - Additional Information (Detail)	12 Months Ended
	Sep. 30, 2016
Derivative [Line Items]
Derivative, term of contract (in months)	1 month
Minimum
Derivative [Line Items]
Derivative, Remaining Maturity	1 month
Maximum
Derivative [Line Items]
Derivative, Remaining Maturity	13 months